1. Field of the Invention
The present invention relates to a magnetic material useful for permanent magnet, bond magnet or other material.
2. Description of the Related Art
As high performance rare earth permanent magnets, hitherto, Sm-Co system magnet and Nd-Fe-B system magnet are known, and their mass production is promoted. These magnets contain Fe and Co at high rates, and they contribute to increase of saturation magnetization. These magnets also contain rare earth elements such as Nd and Sm, and the rare earth elements bring about a very large magnetic anisotropy derived from the behavior of 4f electrons in the crystal field. As a result, the coercive force is increased, and a magnet of high performance is realized. Such high performance magnets are mainly used in electric appliances such as loudspeaker, motor and instrument.
Recently, on the other hand, intermetallic compound having ThMn.sub.12 crystal structure is noticed. This compound is small in the stoichiometric composition of rare earth elements with respect to 3d transition elements, as compared with that of intermetallic compounds belonging to Sm-Co magnet and Nd-Fe-B magnet such as Sm.sub.2 Co.sub.17 and Nd.sub.2 Fe.sub.14 B, and contains large amount of 3d transition elements. It is therefore possible to realize a large saturation magnetization and high maximum energy product. Besides, this compound is small in the composition ratio of expensive rare earth element and may be manufactured at a low cost.
However, in the permanent magnet material composed iron-rich intermetallic compound is produced large amount of impurity phase mainly of .alpha.-Fe. Therefore, the permanent magnet is deteriorated the magnetic characteristic.
Besides, a magnetic material having a composition of introducing the intersticial elements such as N, C, P in the crystal lattice of the principal phase has been developed. This magnetic material is notably improved in the Curie temperature of the principal phase, saturation magnetization and magnetic anisotropy.
In the existing magnetic material introducing the intersticial elements in the principal phase, nevertheless, the thermal stability of the principal phase is poor, and, for example, R.sub.2 Fe.sub.17 nitrogen compound begins to decompose into .alpha.-Fe and rare earth nitride (RN) at 600.degree. C. RFe.sub.11 Ti.sub.1 nitride having ThMn.sub.12 structure begins to decompose at 450.degree. C. Therefore, it is very difficult to form an intersticial element containing compound while suppressing the decomposition thereof, and a dense magnet cannot be formed by hot pressing or sintering heating higher than the decomposition temperature of the magnetic material.